A Temperature-Agnostic 18-MSPS, 12-bit SAR ADC Operating From 50 to 400 K for Space Instrumentation

Abstract

Space instrumentation is typically placed in a shielded “hot box” to protect against extreme-temperature variations, but this compromises size, weight, and power (SWaP). Unshielded instruments on the moon’s surface must operate over a continuous temperature span of 50–400 K. The challenge of wide-temperature operation mostly lies in cryogenic operation due to the onset of carrier freeze-out, and we address this by focusing on the warm temperature limit where foundry-provided models are still valid. By designing at the warm temperature limit and selecting specific circuit and architectural design choices that benefit from operation at lower temperatures, we eliminate the need for cryogenic device models while achieving the full temperature range of operation. For example, we use switching circuits that rely on charge redistribution, which benefit from faster switching at colder temperatures, but at the expense of higher leakage current and reduced switching speed at warm temperatures, rather than static-biased circuits. We demonstrate this in an 18-MSPS, 12-bit ADC that maintains >65-dB SNDR and >75-dBc SFDR across the Nyquist bandwidth and the full 50–400-K temperature range without any temperature-dependent calibration or user input. This ADC is characterized continuously across the full temperature range while being temperature agnostic and achieves a competitive energy efficiency and performance among other wide-temperature ADCs.